A familiar difficulty that occurs in the backing of towed automotive trailers is that of jackknifing--the tendency for the trailer axis to yaw with respect to the towing motor vehicle. In order to minimize jackknifing and cause the trailer to move in a desired direction, the vehicle operator must use the proper sequence of reverse steering maneuvers. If the operator is skilled in this procedure, and if there is adequate room to perform the vehicle steering maneuvers, the trailer can usually be backed satisfactorily. However, if the operator is not skilled in trailer backing, or if the trailer is shorter than the vehicle, the backing process can be quite tedious and time-consuming, particularly if the trailer is to be backed into a precise particular location. Also, if there is inadequate space available for maneuvering the vehicle (due to other vehicles, buildings, curbs, trees, structures, etc.), it may be virtually impossible to back the trailer as desired. Further, if the operator cannot see the trailer adequately, his backing accuracy can be impaired even if he is highly skilled in trailer handling, resulting in a most difficult and time-consuming process.
While the applicant is unaware of any steering systems available for trailers, it appears that a number have been described in the patent art. Of these, U.S. Pat. No. 3,312,480 is perhaps the most pertinent patent of those examined. This patent describes the control of a pair of steerable wheels of a trailer through a cam which has two basic positions of operation which are selected by a castor wheel, which assumes a first position when the towing movement is forward, and a second position when movement is backward. Steering is then effected by a diagonally positioned rod coupled through a specially configured cam to a conventional type tie rod connecting the steerable wheels, the rod being coupled to the rear of the towing vehicle at a point to the side of the basic towing connection between the towing and towed vehicles.
Significantly, the system of U.S. Pat. No. 3,312,480 steers a towed vehicle along a greater arc than that of the towing vehicle. Since it is the arc of the towing vehicle that is controlled by the operator, this disparity is deemed objectionable. Further, the system of this patent is a full-time system, effecting steering while a vehicle is moving in a forward direction as well as in a backward direction. Forward movement is typically at highway speeds wherein trailer steering can create instabilities that may be dangerous.